The key-operated ignition switch that enjoys virtually universal usage in modern automotive vehicles is one that comprises a lock having a barrel with a slot into which a metal key is inserted. If the key is valid, the pattern that has been cut into an edge of its shaft to create the key's teeth sets the lock tumblers so as to just free them from locking engagement with the barrel, thereby allowing the barrel to rotate when the base of the key is turned. Typically, the barrel can be rotated from an Off position selectively to Accessory, On (Ignition), and Start positions to selectively connect various branch circuits of the vehicle's electrical system to the vehicle's electric power supply.
Repeated operation of the ignition switch naturally occasions mechanical wear and in certain types of vehicles, pick-up and delivery vehicles for instance, the ignition switch is operated relatively frequently so that as a result, such a vehicle has a ratio of switch operations to miles traveled that is considerably higher than other types of vehicles, such as heavy trucks and personal cars. Therefore, the life expectancy of an ignition switch in pick-up and delivery vehicles is below average when measured in terms of vehicle miles traveled, and ignition switch replacement is more apt to occur in vehicles that are used for this type of service. Accordingly, an improvement that would extend the life expectancy of an ignition switch would be advantageous for such vehicles since the probability that a switch would need replacement after a given amount of vehicle miles traveled would be reduced. The present invention is directed toward such an improvement.
The invention arises at least in part through the recognition that it is the rotary motion imparted through the key that is a significant contributor to mechanical wear. Hence, the invention avoids such motion, and instead, employs linear motion of a key for selectively operating the switch to its various positions. The inventive switch comprises neither rotary barrel nor tumblers. A preferred embodiment comprises a detent mechanism to define various operating positions, and to the extent that there is any wear, it is only to overcome the detent mechanism as the key is either being inserted into or removed from the switch. The preferred embodiment likewise does not rely on mechanical means of keying, but rather comprises a non-contacting key reader, such as an optical or magnetic reader, for reading a corresponding code that has been imparted to an associated key. In the exemplary switch to be herein disclosed, the detent mechanism comprises means that as the key is increasingly inserted into the switch defines in succession, an Accessory position and an On (Ignition) position. A Start position is reached by inserting the key still further into the ignition switch beyond the On position against a return spring force that is urging the key back toward the On position. In this way the start function is caused to occur in a manner similar to pushing of the separate start push-button switch that was formerly extensively used in the automotive industry when the ignition switch and the start switch were two separate switches on the instrument panel, only the former of which was key-operated. In other words, the present invention contemplates that once the vehicle's engine has started, the releasing of the key will automatically cause the switch to return from the Start position to the On position by virtue of the return spring force, analogous to the start function ceasing when the start push-button in the earlier type of system was released.
An ignition switch that utilizes a non-contacting key reader provides certain advantages over a mechanical key switch. For example, it allows control of certain features or functions, such as lights, latches, and data collection, to occur in conjunction with the operation of the ignition switch. Also, it allows on-line programming of the code into the key, with the possibility of purchasing key blanks in bulk and creating as many or as few keys as needed. The use of a retaining ring and detent mechanism, as hereinafter described, also allows simple and convenient removal of the shaft of a broken key front the switch should such breakage occur while the shaft is in the switch.
The foregoing, as well as further features, advantages, and benefits of the invention, will become apparent as the description proceeds. Drawings accompany the disclosure and represent a presently preferred embodiment of the invention in accordance with the best mode contemplated at this time for carrying out the invention.